This invention relates to an ink jet wherein the ink within the jet is of the phase change type which may be referred to as hot melt ink.
The phase change or hot melt ink of the type utilized in an ink jet is characteristically solid at room temperature. When heated, the ink will melt to a consistency so as to be jettable. A hot melt ink jet apparatus and method of operation are disclosed in copending application Ser. No. 610,627, filed May 16, 1984. The hot melt ink may be jetted from a variety of apparatus including those disclosed in the aforesaid copending application.
It has been found that extended or continuous heating of hot melt ink to a temperature such that the ink is in a liquid state can actually degrade the ink. In other words, the application of heat at an elevated temperature will adversely affect the characteristics of the ink such that both the performance of the ink jet as well as the characteristics of the jetted ink will vary. Such a degradation can adversely affect quality of printing achieved by an ink jet or an array of ink jets.
Because of this degradation of the ink, it has been found to be desirable to cool the ink when the ink jet is in a standby mode, i.e., the ink jet is not being called upon to print. However, hot melt ink will contract upon a phase change from the solid state to the liquid state. Such a contraction can result in the depriming of the ink jet which is, of course, undesirable.